1. Technical Field
Embodiments of the invention relate generally to apparatus and method for transferring a hydrocarbon fluid, e.g. liquefied natural gas (LNG), between two bodies, e.g. a carrier vessel, a floating/fixed hydrocarbon facility.
2. Description of Related Art
Various apparatus and methods for offloading hydrocarbon fluid from a carrier vessel to a floating/fixed hydrocarbon facility, and vice versa, are available but have inherent problems. Offloading hydrocarbon fluid between vessels is also problematic due to unpredictable changes to sea state conditions.
US 2009/0165874 A1 (Pollack et al.) discloses a hydrocarbon transfer system that includes a first structure with a length direction and a transverse direction having a frame carrying a vertical arm with at its end a fluid connecting member for connecting to a second structure which is moored alongside the first structure. The connecting member includes a winch and first guiding elements for engaging with second guiding elements on the second structure by connecting a wire to the winch on one end to the second structure on the other end, and a tension device for moving the vertical arm away from the second structure for tensioning the wire. Due to the inherent rigidity in the above-described members, the system is susceptible to damage if there is a large relative movement between the first and second structures and/or relative dynamic motions are frequent due to severe weather condition. Further, the use of swivels increases a likelihood of leakage during hydrocarbon transfer. This system is also very expensive to manufacture.
US 2010/0147398 A1 (Thomas at al.) discloses a platform and a manifold, the latter being intended to be connected to a fluid tank. The manifold comprises a length of rigid tube defining a pipe of approximately horizontal axis and a length of connecting tube for connection to a transfer line connected to the length of rigid tube. The length of connecting tube is permanently attached to the length of rigid tube and is hinged to the length of rigid tube to allow movement relative to the length of rigid tube between: —a retracted rest position in which the length of connecting tube extends entirely inside the inner edge; and—a first or filling position, in which the free end of the length of connecting tube projects out from the outer edge of the support platform.
In S. Hoog, H. Koch, R. Huhn, C. Frohne, J. Homann, G. Clauss, F. Sprenger, D. Testa: “LNG Transfer in Harsh Environments-Introduction of a New Concept”, OTC 19866, Offshore Technology Conference, Houston, USA, 2009, an approach and handling system is disclosed for use when a carrier vessel and terminal are moored in a tandem configuration. A loading bridge is provided at the terminal to handle four transfer pipes simultaneously by a two part header structure which is transferred between the terminal and carrier vessel. The two part header structure combines the following active functionality: simultaneous support and operation of all four flexible pipes with related Quick Connect/Disconnect Couplers (QCDC) and Emergency Release Couplings (ERC); winch driven fine approach, alignment and landing at the LNGC receiving manifold aided; damping of the touch down at the manifold by means of hydraulic dampeners; operation (closing and disconnection) of all four QCDCs; operation (closing and disconnection) of all four ERCs in an Emergency Shut-Down (ESD) situation; remote controlled departing of both header parts (and subsequent lifting of the upper means of pre-tensioned wires suspended from the loading bridge) in an ESD situation. Normally, the carrier vessel would need to move away from the terminal and hence, in this system, before the carrier vessel can move away to safety, the header structure has to be lifted clear to prevent collision with parts of the carrier vessel.